Q(?) about Power-output related to Impedance's, Wanted to ask this for years!!

K

Kro-1

Audiophyte
#1
Hello, I 'm new here. Quick couple things to say before the Question, I'm not an expert / pro with audio or home audio ..or electronics, I Have More of a basic understanding. (basically I'm very new but I have been doing home theater in a PC/Computer setup for years with home bookshelf speakers and a subwoofer+receiver)

ok so the question (i've wanted to ask for years) is about the power output from your receiver/amplifier related to the impedance of the speaker.
- I've not been sure how to word this question so I'll just wing it. . .

: Does having a lower impedance speaker make it harder for the speaker to be driven? - I ask because my thought on this is, with a capable amplifier, the amplifier would PUSH / PUT OUT more power. if you look at the crown XLS drivecore series 2 amps, they put out more watts at lower ohm. I've seen videos of people talking about how the lower impedance speakers are harder to drive. This is where I'm misunderstanding things(In terms of what they're saying) . . - to me the sensitivity of a speaker is where the output is shown, like power output over distance. dB?

so, . . to elaborate on my question, to be answered in another way.

Which of these speakers would pull/draw more power from the amp, & output louder?( it might be obvious )

Speaker-A: 8ohm // 90dB
Speaker-B: 4ohm // 90dB
 
Matthew J Poes

Matthew J Poes

Full Audioholic
Ratings
221
#2
As the impedance of the speaker drops the current increases. For a given power output, say 50 watts, the lower impedance would have half the voltage and twice the current on a 4 ohm vs 8ohm speaker. If an amplifier could deliver X volt swings and had unlimited current capabilities, then the amp would double its power into 4ohms compared to 8ohms (because the voltage stays constant but the current doubles). This is tough because its easier to deal with high voltage than high current and the transformer size and supply capacitors are the limiting factors for current. Inexpensive receivers and amplifiers have small transformers and thus can't produce the necessary current. Often their output devices also cant swing the higher current so they can become more likely to overheat. A lot of inexpensive receivers include a 8ohm/4ohm switch and what it usually does is actually lower the rail voltage to make it easier for the amplifier modules and power supply to handle the lower impedance.

You have to remember that in your speaker example, this needs to be taken in context. 90 db's at what? 1 watt? 2.83 volts? What kind of 8 ohm load? What kind of 4 ohm load? A speaker might have a nominal impedance of 8ohms, but drop to 3ohms at 30hz with a big swing in the phase. This is harder to drive than a speaker that is a constant 4ohms with no big swings in the phase. The worst case scenario being when the phase angle swings 90 degrees and the amplifier is expected to swing the maximum current as it approaches 0 voltage. I've seen speakers rated at 8 ohms with impedance dropping to 2 ohms in the bass, and 4 ohm speakers that only drop to 4 ohms barely in a bass region. A speakers impedance rating is up to the manufacturer's interpretation of their data.

Sensitivity is typically measured as 1w/1m but companies vary in how they do this. It's usually specified as a voltage, 2.83 volts for 8 ohms and 2 volts for 4 ohms. If a company specifies a 4 ohm speaker at 2.83 volts, it gives the speaker a 3dB sensitivity advantage (since the average consumer doesn't know this, they just think the 4 ohm speaker is more sensitive). Some manufacturers even state the 2.83 volt as 1 watt for a 4 ohm speaker, even though its actually 2 watts. Pretty shady!

In your example above, if both speakers were turned up to their max, assuming all else is equal, the 4 ohm speaker would draw twice as much power. The voltage would be fixed, but the current would double. In practice, its far more complex than this.
 
lovinthehd

lovinthehd

Audioholic Overlord
Ratings
4,514 18 37
#3
Might help to visualize a typical speaker's impedance response vs frequency here's one from a Klipsch speaker
Klipsch RF7 II Impedence Curve.jpg
 
K

Kro-1

Audiophyte
#4
I probably should of stated further not only am I not an audio expert, but my understanding of technicalities with Watts, volts, amps, and whatever else that's involved isn't really there; Maybe I'm below basic meaning I didn't go to school for this, but know how to hook up speakers and have other basic understandings, But when it comes to the technical electrician/audio side of things I think I'm 'SOL', my comprehension of tech side of things isn't great either.

I DO have interest in home audio I plan to do my own home theater when the time comes, and I have more space to do it. ( Hopefully moving early next year..)

Matthew J Poes, I Read your post, Some of it makes sense to me, I'm sure it makes sense to many and is informative to people, I wasn't going to say anything or reply and just say 'f- it, I Don't understand things so why bother,(if I did this, this post would bother me for the rest of time//i.e stress me out)..because I Do want to understand but Have a hard time with it(comprehension). I wish I had gone to school for this stuff knowing now this is a main interest of mine.

-To be honest I don't understand the volt thing, That's one thing my view on your post keeps coming back to(because not understanding it)
- also, swings, or.. volt swings,
- I Still don't understand phase well, I know it's a direction of something.. I know my sub has a phase switch but don't know much about it, I think it can affect the sound in certain situations or with more than one sub(?)- not sure. I usually just keep it on '0'

I've used and own a pair HB-1 MK2 Horn Bookshelf Speaker, I plan to use them in my future HTR, as BACK L+R or maybe REAR L+R. depending on the setup of the room etc..

I Can't post links yet, But if you search for the speaker, google: HSU Research, then look on there for the owners guide/manual you'll find it.

if you look in the manual, these dip / or go into 4 ohm minimum. 6 ohm nominal. I always thought nominal meant average or overall..

I see in the manual it says:
Sensitivity: 92 dB/1m/2.83V rms, half space - the 2.83V like what you're talking about, when I've seen this I've just skipped it b/c I Don't understand it. So.. It's more complex than I've been allowing or thinking.

Without having gone to school for these things or having knowledge already about volts with other audio technical stuff, I Feel stuck to continue my way(not that I want to),pretty much guess work then with the more complex tech stuff involved.

Thanks for your time, and any other future help.
-Kro
 
K

Kro-1

Audiophyte
#6
Might help to visualize a typical speaker's impedance response vs frequency here's one from a Klipsch speaker
View attachment 27285
I Don't understand the chart really,
What does the green Line represent, and the black? This is to show what impedance the speaker is at what frequency? what's the +/- Deg meaning?

Sorry I'm not knowledgeable of this stuff.. Thanks though.
 
Matthew J Poes

Matthew J Poes

Full Audioholic
Ratings
221
#8
I Don't understand the chart really,
What does the green Line represent, and the black? This is to show what impedance the speaker is at what frequency? what's the +/- Deg meaning?

Sorry I'm not knowledgeable of this stuff.. Thanks though.
One is impedance and one is phase. This chart isn’t labeled clearly so it’s hard to tell. To be honest, the electrical phase is a very hard concept to wrap your head around. I recommend not focusing on that right now. I mentioned that to make the point that how demanding a speaker is or an amplifier depends on more than just its impedance.

Nominal is another way of saying average imependance and minimum is minimum. It’s because a speaker can nominally be 8ohms but drop to 4ohms or less and be hard drive. The phase angle, which I mentioned is a tricky concept, is how the current draw following the voltage draw as it swings through the cycle. A speaker that asks the amplifier to deliver peak current and minimum voltage is hard to drive because the amplifier has to deliver so much current.

Those squiggly lines represent the fact that the speakers electrical phase and electrical resistance vary with frequency. This is known as a dynamic load. Impedance is a term for the resistance of a device that is reactive by nature. This means that they are indicative, capacitive, and resistive by nature, rather than purely being on. A resistor, on the other hand, is ideally only resistive. It is not reactive.
 
Matthew J Poes

Matthew J Poes

Full Audioholic
Ratings
221
#9
Keep in mind you can’t expect to learn all of this right away from a few online posts. It takes time. My knowledge of this stuff is not normal and comes from the better part of 30 years learning it. I rebuilt a tube amplifier before I could legally drive.

Just try to take this stuff in best you can. Ask questions. Read articles. It will sink in eventually. Also keep in mind, you don’t have to understand any of this in order to enjoy your system. Knowing the engineering of audio equipment is not a requirement for being knowledgeable of good sound.
 
CB22

CB22

Full Audioholic
Ratings
151 1 1
#10
Without having gone to school for these things or having knowledge already about volts with other audio technical stuff, I Feel stuck to continue my way(not that I want to),pretty much guess work then with the more complex tech stuff involved.
Don't feel bad my friend. Some times I feel the same way about this stuff. I had the same problem with this thing called "Crest Factor". That was a real pain in the ass and ultimately, i just said f- it. Despite all the graphs, math/ engineering let your ears do the judging.
 

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